[Bug 1832795] Re: Race in aufs leads to use-after-free

The task "linux (Ubuntu)" has been closed automatically because requested additional information has not been added. If this issue is still present in a supported Ubuntu kernel, please reopen the task and provide the requested information, and any other updated details. This action was performed by an automated process maintained by the Ubuntu Kernel Team. ** Tags added: kernel-autoclosed kernel-autoclosed-invalid ** Changed in: linux (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/1832795 Title: Race in aufs leads to use-after-free Status in linux package in Ubuntu: Invalid Bug description: SRU Justification Impact: A race in aufs can result in use of a DYNOP object which is being freed after its reference count reaches 0, leading to an oops. Fix: Upstream fix to aufs to ignore objects whose reference count is 0. Regression Potential: Low, limited to aufs and confirmed in testing to fix the issue. --- I have found and reported a critical bug in aufs (as shipped with the latest Ubuntu kernels, both on Bionic and Xenial), which potentially affects anyone running Docker on Ubuntu using aufs graph driver. The fix has been developed, tested at least by me to fix the issue, and committed into upstream aufs git repos The nature of the bug is, in case of multiple parallels aufs mounts and unmounts, the kernel can screw up krefs, and once that happens, the only remedy is to reboot it (as commands like mount/umount or cat /proc/mounts are all stuck in syscalls). I would appreciate syncing aufs with the latest upstream release from git, as it was done a few times already, or at least taking the below fix (whatever suits maintainers better). The fixed versions are the ones marked with 20190610, and from what I see they are available for all kernel versions since 4.14 (for example, 4.15 tree is here: https://github.com/sfjro/aufs4-standalone/commits/aufs4.15). For 4.4, a backport might be needed, but it should be trivial. Original bug report: https://sourceforge.net/p/aufs/mailman/message/36680389/ Fix: https://github.com/sfjro/aufs4-linux/commit/b633d7b2635b9615fe294b85257d05008e3747a3 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1832795/+subscriptions